public class MyLinkedList implements IList{
    static class ListNode{
        public ListNode prev;
        public ListNode next;
        public int val;
        public ListNode(int val){
            this.val=val;
        }
    }
    public ListNode head;
    public ListNode last;
    //头插法
    public void addFirst(int data){
        ListNode node=new ListNode(data);
        if(head==null){
            head=node;
            last=node;
        }else{
            node.next=head;
            head.prev=node;
            head=node;
        }
    }
    //尾插法
    public void addLast(int data){
        ListNode node=new ListNode(data);
        if(head==null){
            head=node;
            last=node;
        }else{
            last.next=node;
            node.prev=last;
            last=last.next;
        }
    }
    //任意位置插入,第一个数据节点为0号下标
    public boolean addIndex(int index,int data){
        ListNode node=new ListNode(data);
        ListNode cur=head;
        int k=0;
        if(index>size()||index<0){
            return false;
        }
        if(index==0){
            addFirst(data);
            return true;
        }
        if(index==size()){
            addLast(data);
            return true;
        }else {
            while (k != index - 1) {
                cur = cur.next;
                k++;
            }
            node.next = cur.next.next;
            node.prev = cur;
            cur.next = node;
            node.next.prev = node;
            return true;
        }
    }
    //查找是否包含关键字key是否在链表当中
    public boolean contains(int key){
        ListNode cur=head;
        if(cur!=null){
            while(cur!=null){
                if(cur.val==key){
                    return true;
                }
                cur=cur.next;
            }
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key) {
        ListNode cur = head;
        while (cur != null) {
            if(cur.val == key) {
                if(cur == head) {
                    head = head.next;
                    if(head == null) {
                        last = null;
                    }else {
                        head.prev = null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next == null) {
                        last = last.prev;
                    }else {
                        cur.next.prev = cur.prev;
                    }
                }
                return;
            }else {
                cur = cur.next;
            }
        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        ListNode cur=head;

        while(cur!=null){
            if(cur.val==key){
                if(cur==head){
                    head=head.next;
                    if(head==null){
                        last=null;
                    }else{
                        head.prev=null;
                    }
                }else{
                    cur.prev.next=cur.next;
                    if(cur.next==null){
                        last=last.prev;
                    }else{
                        cur.next.prev=cur.prev;
                    }
                }
            }
            cur=cur.next;
        }
    }
    //得到单链表的长度
    public int size(){
        ListNode cur=head;
        int k=0;
        while(cur!=null){
            k++;
            cur=cur.next;
        }
        return k;
    }
    public void display(){
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val+" ");
            cur = cur.next;
        }
        System.out.println();
    }
    public void clear(){
        head=null;
        last=null;
    }
}
